System and method for determining atomization characteristics of spray liquids

ABSTRACT

A system and method for determining the atomization characteristics of fluids being emitted by a nozzle is disclosed. In one embodiment, a fluid is emitted through a nozzle while simultaneously sensing vibrations occurring within the nozzle. The vibrations provide information about the atomization characteristics of the fluid. By comparing the sensed vibrations to vibration patterns produced by known fluids through the same or a similar nozzle, the atomization characteristics of the fluid being tested can be predicted. In one embodiment, for instance, the atomization characteristics of a fluid may be determined as a function of velocity or flow rate through the nozzle.

BACKGROUND OF THE INVENTION

The performance of spraying systems, as measured by the droplet sizespectra and distribution pattern of the spray is highly dependent on thefluid properties of the liquid being sprayed. The classic fluidproperties such as density, equilibrium surface tension, dynamic surfacetension, shear viscosity, extensional viscosity, void fraction ofincorporated gasses, etc., all affect the behavior of the liquid as itpasses through an atomizer, and subsequently, the characteristics of theresulting spray. When sprays are produced for coating, drying and otherprocesses, the spray characteristics are critical factors in theperformance of the process and using the spray and the resulting qualityof the product.

To achieve desired spray characteristics, the proper nozzle or atomizermust be selected and the optimal operating conditions of the atomizerand fluid handling system must be determined for the fluid to beatomized. Selection of the nozzle and determination of the operatingconditions can be an extensive, iterative, experimental process due tothe complexity of the fluid—atomizer interaction. Especially for complexfluids that are heterogeneous, non-Newtonian or otherwise difficult tocharacterize, a priori predictions of sprayer performance can bedifficult and inaccurate. Subsequent changes in the fluid composition,wear in the atomizer or other departures from the original testconditions can require repeat experiments.

Laboratory measurements of fluid properties can be tedious, expensiveand time consuming. Additionally, the measurements are often made usingstandardized techniques that do not closely approximate the conditionsin the actual spraying process. These conditions can include turbulencein the flow system, shear rates during flow and atomization, spatial andtemporal gradient in temperature, reactions in the fluid, etc.

Likewise, the measurement of spray characteristics such as droplet sizespectra, spatial distributions and patterns and droplet velocitiesrequires specialized, expensive equipment and technical expertise inproper sampling in data interpretation. With limited feedback onatomizer performance, especially in processes where the sprays orproducts are not visible to system operators, generation of poor qualitysprays with undesirable characteristics is often undetected untiladverse consequences have occurred.

While these challenges are present for any spraying applications, aparticular problem exists for agricultural spraying where the sprayfluids can be mixtures of pesticides, fertilizers, surfactants,shear-inhibitors, buffers, adhesives and other supplemental agents knownas spray adjuvants. These mixtures are highly variable and often createdfor specific fields to be treated; the physical properties of thesemixtures are very complex and it is difficult to predict how the fluidmixtures will behave in a given spray system.

Spray drift, or the inadvertent movement of small spray droplets fromthe target site to a non-target area, is a significant issue presentlyfacing agricultural applicators throughout the United States. Thestrongly related issues of spray quality, that is, coverage of thetarget and efficacy of the product against the target pests are also ofgreat concern. Agricultural applicators desire to use the best driftmanagement methods and equipment to provide the safest and mostefficient applications of pest control materials to the targeted pest.They are responsible for making good decisions in the field on a dailybasis. Spray droplets that drift off-site or are not correctly appliedto the target crop or pest represent wasted time, resources and resultin environmental pollution. This results in increased costs for the cropgrower and, subsequently, to the consumer. In addition, materials suchas herbicides and defoliants that drift off-site can result in a seriousfinancial liability if surrounding crops are damaged.

The minimization of off-site movement of agricultural sprays is to thebenefit of all concerned—applicators, farmers, regulators, the publicand the environment. Applicators need additional methods and equipmentto balance or optimize spray tank adjuvant performance and economics toachieve drift mitigation goals for a given application. In particular, aneed currently exists for an apparatus and method for assistingapplicators in determining the best possible application parameters tohelp meet product instructional label criteria and mitigate spray drift.

It has long been understood that spray droplet size is the mostimportant variable in spray coverage, performance and spray driftcontrol or mitigation. For an agricultural spray dispensed from anaircraft, spray nozzle selection is the first factor considered whenattempting to influence the spray droplet spectrum. Second are theoperational factors that influence atomization. These include nozzleangle or deflection to the airstream, aircraft speed, and spray liquidpressure. Spray tank additives or adjuvants play an auxiliary role inspray droplet spectra. There are currently over 416 adjuvants marketedin California alone according to Crop Data Management Systems(Marysville, Calif.). Adjuvants are classified as surfactants,spreaders, stickers, deposition aids, activators, humectants,antifoamers, wetting agent, and drift reduction agents. These agents areadded to the spray tank mix that may include a number of activeingredients in the pesticide formulations.

Adjuvants can aid in the product making better contact with the pest byspreading it over the leaf surface or the body of the insect pest.Adjuvants can also reduce the likelihood of the product dripping off theleaf onto the ground. Similarly, excessive or incorrect adjuvant use cancause the product to drip or run off the leaf. Adjuvants also can bevery useful in helping the product “stick” to the leaf or crop,preventing runoff during rain or irrigation. Finally, adjuvants areoften marketed as drift reduction agents. The addition of an appropriateadjuvant can tend to increase droplet size, which generally reducesdriftable fines. Unfortunately for applicators, sometimes recommendedmixtures are found to be “poor combinations”, even if applied under“ideal climatic conditions”, when damage to crops, crop losses and driftproblems are experienced.

Droplet size is determined by the physical properties of the componentsof the droplet fluid—in this case, the tank mix, usually composed ofwater, pesticide active ingredient formulations and adjuvant(s). The keyproperties of the tank mix that have a significant effect on dropletsize and the resulting atomization profile are: dynamic and equilibriumsurface tension, extensional viscosity, and shear viscosity. Each timethe applicator adds something to the tank mix, the physical propertiesof that tank mix change and that changes the atomization profile.Because of the continued development and advancements in adjuvants, aneed also exists for a system and method for assisting applicators inmaking sound decisions about the addition of these products and thesubsequent impact their addition will have on the actual application,both for spray quality and for drift potential.

What is needed by all applicators, not just aerial but also for fieldcrop boom applicators and orchard and vineyard air carrier applicators,is a field method to estimate the atomization characteristics ofparticular spray mixes that they are about to apply, especially if themix is used only occasionally. By knowing the atomizationcharacteristics of the mix, one can then choose the proper nozzle andspray conditions to avoid drift and optimize deposit and efficacy. Onemay even, upon getting the information, decide to delay an applicationuntil better environmental conditions exist.

In a broader sense beyond pesticide spraying, optimizing any sprayingsystem requires that the atomizing properties of the fluid be known. Thecomplexity of fluid properties and the complexity of the fluid-nozzleinteraction make the prediction of the atomizing properties fromlaboratory measurements of individually-measured fluid properties (e.g.,dynamic and equilibrium surface tension, shear viscosity, extensionalviscosity, density, etc.) difficult and inaccurate. The difficulty ofselecting and conducting the most appropriate laboratory tests of thefluid properties, combined with the uncertainty of prediction models ofdroplet size spectra from the resulting measurements, lead to the needfor a more direct and simple method for the end user to determineatomization characteristics of a fluid before undertaking a sprayoperation.

SUMMARY OF THE INVENTION

The present disclosure is directed toward a system and method tocharacterize the atomization properties of fluids in order to select,optimize, maintain and control the proper nozzle and spray conditions toachieve a desired spray with specified properties. Additionally, thesystem may be used to determine if changes in a fluid mixture willproduce significant changes in the fluid behavior as it passed throughan atomizer. By characterizing the atomization properties of fluids, thepresent disclosure allows a user to control droplet size and dropletspectra in order to minimize drift and to assist in applying the fluidonto a target site.

In one embodiment, the system of the present invention can include anorifice or nozzle similar or identical to a spray nozzle to be used forspraying. The fluid is excited by being forced through the nozzle undera controlled pressure or controlled flowrate and the resultingvibrations of the fluid sheet or jet are detected by a sensor. Thesensor is in communication with a controller that determines thecharacteristics of the vibration. These characteristics can include themagnitude of the vibrations, the directions of the vibration, thespectral composition of the vibrations, the transmission of thevibrations through the fluid or combinations of the characteristics. Inone embodiment, the sensed characteristics of a fluid to be tested arecompared to the characteristics measured for a fluid of knowncomposition and atomization properties. The relative atomizationproperties are then determined.

In one embodiment, the test orifice and the flowrate of the test fluidare adjusted to approximate known atomization regimes such as thoseshown in FIG. 1. The flow rates and orifice diameters are adjusted tocover a working range of the dimensionless numbers, Reynolds (Re), Weber(We) and Ohneserge (Oh), that define the fundamental map of atomization.(Re=Dvρ/μ; We=Dv²ρ/σ; Oh=We^(1/2)/Re where D=characteristic diameter,v=characteristic velocity, ρ==fluid density, μ=fluid viscosity andσ=fluid surface tension). When fluid properties are unknown, thesenumbers can be estimated from a priori knowledge or approximated withvalues from similar fluid.

In one embodiment, a positive displacement pump is in communication withthe controller and is adjusted to vary the fluid flow rate through theorifice in a programmed sequence, representing a range of fluidvelocities through the orifice. The microcontroller receives thevibration data from the sensor simultaneously and determines the fluidvibration properties as a function of the liquid velocity and flowratethrough the orifice.

In general, the method of the present disclosure for determining theatomization characteristics of a fluid being emitted by a nozzleincludes the steps of first emitting a fluid from a nozzle at controlledconditions. Vibrations occurring within the fluid nozzle are then sensedwhile the fluid is being emitted. The sensed vibrations are thencompared to the vibrations of a known fluid having known atomizationproperties for determining the relative atomization properties of thefluid being emitted from the nozzle. The controlled conditions at whichthe fluid is emitted from the nozzle may include a known flow rate,temperature, pressure, and the like. The controlled conditions can beknown by placing various sensors within the fluid flow path. Forinstance, the system may include a flow meter, one or more temperaturesensors, and one or more pressure sensors that are each placed incommunication with a controller that also receives the sensed vibrationsin determining the relative atomization properties of the fluid. Thecontroller may be, for instance, one or more microprocessors.

In one embodiment, the method may include the step of sensing a fluidpressure drop over an orifice while the fluid is being emitted from thenozzle. The pressure drop may be communicated to a controller fordetermining a fluid shear viscosity and a density of the fluid. Theorifice over which the pressure drop is sensed may comprise the nozzleitself or may be positioned upstream from the nozzle.

In addition to sensing fluid pressure over an orifice, a fluid pressuredrop may also be sensed over a tortuous path through which the fluidflows. The tortuous path may be positioned upstream from the nozzle and,in one embodiment, may comprise a packed bed. By sensing the pressuredrop over the tortuous path, a fluid extensional viscosity may bedetermined.

In one embodiment, the vibrations that are sensed from the nozzle areconverted into a spectral density that is used to determine a powerspectrum. The power spectrum is then compared to the power spectrum ofone or more reference fluids for determining the relative atomizationproperties of the fluid. For example, in one embodiment, the sensedvibrations are compared to the vibrations of a plurality of knownfluids. The known fluids may include, for instance, a relatively lowviscosity fluid, a relatively high viscosity fluid, and a fluid having aviscosity in between the relatively low viscosity fluid and therelatively high viscosity fluid.

Once the relative atomization properties of the fluid are determined,one can select a nozzle and operating conditions for emitting the fluidfrom the selected nozzle in a fluid application process as desired.Basically, the atomization properties of the fluid may be determined forany suitable process in which the fluid is to be emitted from a nozzle.In one particular embodiment, for instance, the atomization propertiesof the fluid are determined for applying the fluid in an agriculturalprocess. The fluid, for instance, may comprise a pesticide, a herbicide,a fertilizer, or any other similar material. In agricultural processes,for example, the fluid may be emitted from a nozzle that is mounted to aboom that is in turn pulled by a tractor or may be emitted by a nozzlemounted to an aircraft.

In general, any suitable device may be used in order to sense the nozzlevibrations as the fluid is being emitted from the nozzle. For example,in one embodiment, an accelerometer may be used. The accelerometer maysense vibrations in a single direction or in multiple directions.

In one embodiment, the fluid is emitted through the nozzle and into aspray chamber. An optical device, such as any suitable camera, may beused to optically inspect a flow pattern being emitted by the nozzle.The flow pattern may be further used to characterize the atomizationcharacteristics of the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the classic map of liquid atomization regimes showingpredominant mode of breakup versus the orifice flow nondimensionalnumbers, Re and We;

FIG. 2 is a plan view of one embodiment of a system made in accordancewith the present invention;

FIG. 3 is a perspective view of one embodiment of a vibration sensorattached to a nozzle for use in accordance with the present invention;

FIG. 4 is a graphical representation of the results obtained in Example1;

FIGS. 5A and B represent a side view and a perspective view of thenozzle tested according to Example 2 below; and

FIGS. 6-14 are graphical representations of the results obtained inExample 2.

DETAILED DESCRIPTION

In general, the present invention is directed to a system and processfor determining the atomization properties of complex fluids without theneed for direct measurement of physical properties or spray droplet sizespectra, spray pattern or droplet velocities. More particularly, in oneembodiment, the fluid to be characterized is pumped through an orificeand the resulting vibration of the fluid flow is measured by a sensor.In one embodiment, the pressure drop of the fluid across the testorifice is simultaneously measured in order to provide an estimate ofthe shear viscosity of the fluid and the pressure drop across a tortuouspath, such as across a packed bed of screens, is measured in order toprovide an indication of the extensional viscosity.

In one embodiment, the system may be designed to be sufficiently simpleand small so that sprayer operators in industries such as agriculturalfield spraying can use the system in field conditions using only a smallsample of the spray fluid to be dispensed. After characterization of thefluid, they can select the optimal spray nozzle or operating conditionsto produce the desired spray characteristics. For example, they may usethe system to test a spray liquid mixture composed of various componentsin order to select a nozzle to minimize spray drift during applicationto a field. It should be understood, however, that in addition toagricultural applications, the method and system of the presentinvention may be used to characterize and determine the atomizationproperties of fluids in any suitable process in which the fluid is to beemitted from a nozzle. For example, in one embodiment, the method andsystem of the present invention may be incorporated into a paintspraying operation.

Referring to FIG. 2, one embodiment of a system made in accordance withthe present invention is shown. As illustrated, the system includes asupply reservoir 10 in which the fluid to be tested is contained. Ingeneral, any suitable fluid may be tested in accordance with the presentinvention. The fluid, for instance, may contain various ingredientsincluding suspended particles. Further, the fluid may be adapted for usein any process as desired. For example, in one embodiment, the fluid maycomprise a pesticide, herbicide or fertilizer that is to be appliedduring an agricultural spray process. In an alternative embodiment, thefluid may comprise a fuel. For instance, the present invention may beused to characterize the atomization properties of fuels when the fuelsare being injected into an engine.

The fluid contained in the supply reservoir 10 is pumped from the supplyreservoir in this embodiment by a pumping device 12. In general, anysuitable pumping device may be used. In one embodiment, for instance,the pumping device 12 may comprise a positive displacement pump that iscapable of pumping the fluid from the supply reservoir in controlledamounts. As shown in FIG. 2, the fluid contained in the supply reservoiris pumped through a test nozzle 14 to produce a sheet, jet or spray 16that may optionally be collected in a collection reservoir 18.

In order to ensure that the fluid is pumped through the system at acontrolled temperature, the supply reservoir may be placed incommunication with a temperature control unit 20 that is configured tomaintain the fluid at a specified temperature. Alternatively, atemperature sensor may be placed within the system in order to simplyknow the temperature of the fluid as it is being emitted by the nozzle14.

In accordance with the present invention, a vibration sensor 22 isplaced in association with the nozzle 14 for sensing vibrations withinthe nozzle as the fluid is being emitted by the nozzle.

The vibration sensed by the vibration sensor 22 can provide muchinformation about the properties of the fluid and specifically theatomization properties of the fluid being emitted by the nozzle. Forinstance, it is known that flowing fluids that interact with structuresor nozzles produce characteristic vibrations. The fundamental process isthe periodic separation of the boundary layer of flow passed anystructure with sufficiently bluff trailing edges. The fluid propertiesof surface tension (dynamic and equilibrium) and viscosity (shear andextensional or elongational) affect the behavior of the fluid flow andbreakup. Of particular significance, the vibrational frequencies thatare sensed along with certain vectors of the vibration provide flow rateand droplet size information about the fluid as it is emitted from theparticular nozzle.

In general, any suitable fluid nozzle may be monitored according to thepresent invention. For instance, the fluid nozzle may emit a fan-typespray pattern or a conical spray pattern. Different nozzles will emitcertain frequencies of vibration. Thus, the reference nozzle shouldgenerally be similar to the test nozzle.

In addition to testing different types of nozzles, both continuouslyflowing fluid nozzles and pulsed fluid nozzles may be used in the systemand process of the present invention. When used in conjunction withpulsed nozzles, the vibration analysis is capable of separatingvibrations due to atomization properties from vibrations due topulsation.

Examples of nozzles that may be used as test nozzles in the system ofthe present invention include metering orifice plates that arecommercially available from the TeeJet Company. The orifice plates areavailable in a range of sizes from 0.008 inches to 0.250 inches indiameter. The metering plates represent an abrupt, sharp orifice.Straight stream nozzles may also be used and are available from theSpraying Systems Company. Such straight stream nozzles are available inorifice diameters of from 0.041 inches to 1.375 inches and provide asmooth flow transition prior to the orifice. In still anotherembodiment, fan nozzles may be used to produce liquid sheets. Industrialfan nozzles are available in fan angles of 15°, 25°, 40°, 50°, 65°, 73°,80°, 95°, 110°, and the like. The fan nozzles can have an equivalentorifice diameter of 0.011 inches to 1.375 inches.

Air inclusion nozzles may also be used. Air inclusion nozzles produce amore complex flow passageway and are commonly used in the groundapplication industry. Air inclusion nozzles typically produce vibrationprofiles that have an amplitude approximately two orders of magnitudegreater than conventional nozzles. Air inclusion nozzles are alsosensitive to flow conditions such as nozzle clogging.

When testing fluids for agricultural spray applications, typically thespray nozzles include fan nozzles that have flow angle ranges from 40°to 110° and flow ranges from about 0.1 gallons per minute to 1.0 gallonsper minute (at 40 psi standard pressure).

In one embodiment, flow conditioning sections may be incorporated intothe system in order to produce low turbulence as the fluid enters thenozzle area. Flow conditioning can be as simple as a straight section ofsmooth tube or may include more orifice diameters upstream of thenozzle. Alternatively, an array of straightening tubes constructed of,for instance, thin wall stainless steel tubing, can be packed to createmore laminar flow section prior to nozzle.

Referring to FIG. 3, one exemplary embodiment of a fan nozzle 30 thatmay be used as a test nozzle in accordance with the present invention isshown. Nozzle 30 as illustrated in FIG. 3 is a typical nozzle used inagricultural applications.

As also illustrated in FIG. 3, a vibration sensor 32 is mounted on thenozzle for sensing vibrations. Various different types of vibrationsensors may be used in accordance with the present invention. Forexample, in one embodiment, an accelerometer may be used. The vibrationsensor may be configured to sense vibrations in a single direction, orin multiple directions, such as triaxial accelerometers.

When sensing vibrations in multiple directions, it has been discoveredthat each direction may provide different information regarding theproperties of the fluid and/or the properties of the nozzle. As shown inFIG. 3, as used herein, the Z-axis or direction comprises the directionof flow of a fluid through the nozzle. For instance, if the nozzle ispointing downward, the Z-axis comprises a vertical line. The X-axis, onthe other hand, is perpendicular to the Z-axis and extends to the leftand right of the nozzle when facing a front of the nozzle. The remainingaxis, the Y-axis, is perpendicular to the Z-axis and to the X-axis. Whensensing vibrations, the Y-axis typically provides information related toatomization and spray quality. The Z-axis provides information relatedto flow rate, while the X-axis provides information related to pulsevalve operation when the valve is pulsating.

Some examples of vibration sensors that may be used in the presentinvention include any suitable accelerometer including piezoelectricfilms.

Referring back to FIG. 2, the vibration sensor 22 may be placed in anyappropriate location on the nozzle 14 for sensing vibrations. Forinstance, the vibration sensor 22 can be placed on the nozzle housingor, alternatively, can be otherwise incorporated into the body of thenozzle. In some applications, it has been found that the vibrationsensor can also be placed upstream from the nozzle and still be capableof registering vibration frequencies.

Once the vibration sensor 22 measures vibrations from the fluid nozzle14, the signal created by the sensor is fed to a controller 24 foranalysis. The controller 24 may comprise, for instance, a microprocessoror a plurality of microprocessors. The controller 24, for instance, maybe used to determine peak vibration, duration of vibration and thespectral composition of the vibration. In one embodiment, for instance,the signal created by the vibration sensor 22 can be manipulated andconditioned. For example, the nozzle vibration can be measured and aspectral analysis, such as a Fast Fourier Transform, is conducted todetermine a power spectrum. The power spectrum can then be analyzed andcompared to the power spectrum of a reference fluid that has knownatomization properties. In this manner, the atomization properties ofthe fluid being fed through the system can be determined.

In one particular embodiment, for instance, the controller 24 may storethe atomization properties of multiple fluids that each have differentviscosities. For instance, the controller may include the atomizationcharacteristics of a reference fluid having a relatively low viscosity,a reference fluid having a relatively high viscosity, and a referencefluid that has a viscosity in between the relatively low viscosity fluidand the relatively high viscosity fluid. Of course, the atomizationcharacteristics of many other fluids may be stored within themicroprocessor 24. By comparing the vibration patterns of the fluidbeing emitted by the nozzle 14 to the known atomization properties ofthe reference fluids, relatively accurate estimations can be maderegarding droplet size and/or the spray pattern of the fluid as afunction of flow rate and process conditions.

As shown in FIG. 2, the system of the present invention can furtherinclude a flow meter 26 and one or more pressure sensors 28. The flowmeter may be placed in communication with the controller in order toprovide the controller with the flow rate of the fluid being emittedthrough the nozzle 14. As also shown, the controller 24 may be used tocontrol and receive information from various other components in thesystem. For instance, the controller 24 may receive information andcontrol the pumping device 12 and may receive information or control thetemperature control unit 20.

The pressure sensor 28 as shown in FIG. 2 may also be in communicationwith the controller 24. The pressure sensor 28 in one embodiment, maydetermine the pressure drop of the fluid across the nozzle 14. Whencoordinated with the pumping device 12, the pressure drop versus flowrate information provides an estimate of the fluid shear viscosity anddensity independently from the fluid vibration data.

Instead of measuring the pressure drop across the nozzle 14, in analternative embodiment, an orifice may be positioned upstream from thenozzle 14. The pressure sensor 28 may determine the pressure dropagainst the orifice for also determining fluid shear viscosity anddensity.

In still another embodiment of the present invention, this system caninclude a tortuous path positioned in between the supply reservoir 10and the fluid nozzle 14. The tortuous path, for instance, may comprise apacked bed, such as a packed bed of screens. An additional pressuresensor may be positioned to determine the pressure drop of the fluidover the tortuous path. When coordinated with the pumping device 12and/or the flow meter 26, the pressure drop over the tortuous pathversus flow rate information provides an estimate of the fluidextensional viscosity independently from the fluid vibration data.

When the system includes the pressure sensor 28 as shown in FIG. 2, asdescribed above, information from the pressure sensor and the flow meter26 may be used in conjunction with the geometry of the nozzle 14 tocharacterize the shear viscosity of the fluid. A simple equationrelating flow rate of a fluid through an orifice to the pressure dropthrough the orifice is m=C_(d)Δ_(t)(2ρΔp/)^(1/2) where m=mass flowrate,C_(d) is a drag coefficient related to the fluid and the orificecharacteristics and A_(t) is a characteristic of the test nozzle 14,Δp=the measured pressure drop across the orifice and ρ=the density ofthe fluid. The C_(d) term is a function of Reynolds Number (Re=Dvρ/μwhere D=characteristic diameter, v=characteristic velocity, ρ=fluiddensity and μ=fluid viscosity). When the test nozzle 14 is installed,the orifice characteristics are known. Therefore, knowing the flowratefrom the flowmeter and the pressure drop across the orifice from thepressure sensor, a term for the fluid density and viscosity can becalculated using iteration. This information can be used incharacterizing the fluid, especially when considered in conjunction withthe vibration data from flow through the orifice.

As described above, in one embodiment, the vibration informationreceived from the vibration sensor may be converted into a powerspectrum for comparison to the power spectrum of various referencefluids under similar conditions. For many nozzles, such as especiallynozzles used in the agricultural industry, the nozzles producecharacteristic vibrations in the range of from about 4 kHz to about 6kHz bands. In general, a higher power spectrum indicates betteratomization and usually smaller droplet size.

In one embodiment, the pumping device 12 as shown in FIG. 2 may beconfigured to vary the flow rate of the fluid being tested in aprogrammed sequence. For instance, the controller 24 may be placed incommunication with the pumping device 12 for varying the flow rate in apredetermined manner. By varying the flow rate in a programmed sequence,vibrations generated by the fluid flowing through the nozzle can bedetermined as a function of velocity. In this manner, the atomizationproperties of the fluid can be determined also as a function of velocityand/or flow rate with respect to the test nozzle.

In addition to the vibration sensor 22 as shown in FIG. 2, the systemcan further include an optical sensor positioned to observe the spraypattern 16 that is emitted from the nozzle 14. In general, any suitableoptical sensor may be used, such as an array of LED lights inconjunction with light sensors, or may comprise one or more cameras. Theoptical sensor may be configured to inspect the spray or sheet 16 beingemitted from the nozzle to determine or measure the shape of the spray.For instance, a narrow spray width may indicate larger droplet size.This information can then be used in conjunction with the informationreceived from the vibration sensor.

The present invention may be better understood with respect to thefollowing examples.

EXAMPLE NO. 1

A number of fluids were sprayed through a TeeJet XR11004 fan nozzle. Thefan nozzle tested had a 110° flow angle which refers to the extent ofthe fan-like shape within the X-Z axis plane. The nozzle also had a 0.4gallon per minute flow rate at 40 psi liquid supply pressure. Fluid wassupplied to the nozzle at 40 psi (276 kPa). A single chip accelerometer(Analog Devices ADXL 311) was mounted on the nozzle body to sense thevibration along the axis normal to the fan (the “Y” axis as shown inFIG. 3). Data were collected for 2 seconds and a Discrete FourierTransform was performed on the data by an on-board microprocessor toproduce the power spectrum of the signal.

Results for tap water, a viscous fluid (thick sugar syrup), a lowsurface tension fluid (water+1% dishwashing detergent) and a fluid withpolymer-like properties (fat free salad dressing—with guar gum and otherthickeners) are shown in FIG. 4. Differences in the spectra for thefluids were apparent, especially in the 2.5-4.5 and 5-8 kHz frequencybands and when considering that the dB response axis is a log scale.

As shown by the results in FIG. 4, a relationship does exist betweenfrequency and viscosity of fluids being emitted by a nozzle.

EXAMPLE NO. 2

The potential simplicity and an inexpensive embodiment of the inventionwas demonstrated using a manually-actuated piston pump and close-coupledspray nozzle as shown in FIG. 5. A triaxial accelerometer (PCB Model356A22) was coupled to the outlet of the spray nozzle. The integratedpump was a positive displacement piston pump that dispensed 0.8ml/stroke. The nozzle was a fixed orifice producing a hollow cone spray.Four fluids were tested to determine the vibration characteristics andthe resulting spray droplet size, as visualized by adding a dye to thespray liquid and photographing the spray deposit.

The reference fluid was municipal water. The test fluids were 40% ethylalcohol, a commercial spray surface cleaner (Formula 409) and glycerin.Results for water appear in FIG. 6; results for ethyl alcohol appear inFIG. 7; results for the spray cleaner appear in FIG. 8; and results forglycerin appear in FIG. 9. A clear relationship between the relativepower in the 4-6 kHz frequency band and the resulting spray droplet sizewas observed.

For each of the test fluids, an image of the spray deposit was capturedand the resulting droplet size spectra based on number counts of dropletstains in the image was recorded. Specifically, the spray depositionpattern and the droplet size spectra for water is shown in FIG. 10, thespray deposition pattern and droplet size spectra for ethynol is shownin FIG. 11, and the spray deposition pattern and droplet size spectrafor the cleaner is shown in FIG. 12. Glycerin, on the other hand, failedto atomize and did not produce a spray at all.

As can be shown in FIGS. 10-12, water had a very small droplet size thatwas smaller than the droplet size of the ethyl alcohol and smaller thanthe droplet size of the spray cleaner. The droplet size of the ethylalcohol was smaller but comparable to the droplet size of the spraycleaner. Thus, as shown in FIGS. 6-9 in comparison to FIGS. 10-12, asthe power increased, the droplet size decreased. The glycerin was notatomized by the pump-nozzle combination; the resulting vibration dataindicated virtually no vibration in the 4-6 kHz band.

From the deposition images for water, ethynol and spray cleaner, thesize distribution of the stains on the target paper were analyzed byimage analysis, a common technique used to measure and characterizespray deposition. The number of stains in a representative area oftarget were categorized by size and counted to produce the resultsillustrated in FIG. 13.

As shown in FIG. 13, from the distribution, the fraction of droplets (bynumber) below a cutoff size of 100 microns was determined. This numberwas then compared to the spectral density of the vibrations illustratedin FIGS. 6, 7 and 8. The areas under the vibration curves of the powerspectra were integrated over the range of 4-6 kHz, the frequency bandmost closely associated with the atomization. The relationship betweenthe fraction of droplets and the small size ranges and the totalvibration in the 4-6 kHz range is shown in FIG. 14. A strongrelationship between vibration and droplet size spectra can be seen.

These and other modifications and variations to the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention, which ismore particularly set forth in the appended claims. In addition, itshould be understood that aspects of the various embodiments may beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only, and is not intended to limit the invention sofurther described in such appended claims.

1. A method for determining the atomization characteristics of a fluidbeing emitted by a nozzle comprising: emitting a fluid from a nozzle atcontrolled conditions; sensing vibrations occurring within the fluidnozzle while the fluid is being emitted; and comparing the sensedvibrations to the vibrations of a known reference fluid having knownatomization properties for determining the relative atomizationproperties of the fluid being emitted from the nozzle.
 2. A method asdefined in claim 1, wherein the controlled conditions comprise a knownflow rate.
 3. A method as defined in claim 1, wherein the fluid isemitted from the nozzle at varying flow rates according to apredetermined sequence.
 4. A method as defined in claim 1, furthercomprising the step of sensing a fluid pressure drop over an orificewhile the fluid is being emitted from the nozzle, the pressure dropbeing used to determine a fluid shear viscosity of the fluid.
 5. Amethod as defined in claim 4, wherein the orifice is part of the nozzle.6. A method as defined in claim 4, wherein the orifice is positionedupstream from the nozzle.
 7. A method as defined in claim 1, wherein thefluid is passed through a tortuous path upstream from the nozzle, themethod further comprising the step of sensing a pressure drop over thetortuous path for determining a fluid extensional viscosity of thefluid.
 8. A method as defined in claim 7, wherein the tortuous pathcomprises a packed bed.
 9. A method as defined in claim 2, wherein theflow rate is determined by a flow meter.
 10. A method as defined inclaim 2, wherein the controlled conditions further comprise emitting thefluid from the nozzle at a known temperature.
 11. A method as defined inclaim 1, wherein the sensed vibrations are converted into a spectraldensity that is used to calculate a power spectrum, the power spectrumbeing compared to the power spectrum of the known reference fluid.
 12. Amethod as defined in claim 1, wherein the sensed vibrations are comparedto a plurality of known reference fluids, the plurality of knownreference fluids including a relatively low viscosity fluid and arelatively high viscosity fluid.
 13. A method as defined in claim 1,further comprising the step of selecting a nozzle and operatingconditions for emitting the fluid from the selected nozzle in a fluidapplication process based upon the determined atomization properties ofthe fluid.
 14. A method as defined in claim 13, wherein the fluidapplication process comprises an agricultural spraying process.
 15. Amethod as defined in claim 1, wherein the determined atomizationproperties of the fluid comprise determining a droplet size of the fluidthrough the nozzle as a function of flow rate or velocity.
 16. A methodas defined in claim 1, wherein an accelerometer is used to sense thevibrations.
 17. A method as defined in claim 1, wherein the fluid nozzleincludes a Z-axis that comprises the direction of flow of the fluidthrough the nozzle, an X-axis that is perpendicular to the Z-axis andextends to the left and right of the nozzle when facing a front of thenozzle, and a Y-axis that is perpendicular to the Z-axis and the X-axis,the vibrations being sensed in at least the Y-axis direction.
 18. Amethod as defined in claim 1, further comprising the step of opticallyinspecting a flow pattern being emitted by the nozzle in order tofurther determine the atomization properties of the fluid being emittedfrom the nozzle.
 19. A method as defined in claim 13, wherein theatomization properties of the fluid are determined remote from thelocation of the fluid application process.
 20. A method as defined inclaim 1, wherein the sensed vibrations are communicated to a controllerthat automatically compares the sensed vibrations to the vibrations ofthe known reference fluid.
 21. A system for determining the atomizationcharacteristics of a fluid comprising: a supply reservoir for holding afluid, said reservoir including an outlet for dispensing the fluid; apumping device for pumping the fluid from the supply reservoir; a nozzleplaced in communication with the supply reservoir for receiving thefluid, the fluid being pumped from the supply reservoir by the pumpingdevice through the nozzle; a vibration sensor for sensing vibrationsoccurring within the fluid nozzle as the fluid is being emitted by thenozzle; and a controller in communication with the vibration sensor forreceiving a spray pattern vibration output from the vibration sensor,the controller being configured to compare the sensed vibrationsreceived from the vibration sensor to the vibrations of a knownreference fluid having known atomization properties for determining therelative atomization properties of the fluid being emitted from thenozzle.
 22. A system as defined in claim 21, wherein the controller isconfigured to control the pumping device for varying the flow rate ofthe fluid through the nozzle according to a predetermined sequence, thecontroller being further configured to determine the relativeatomization properties of the fluid being emitted from the nozzle as afunction of flow rate.
 23. A system as defined in claim 21, furthercomprising a pressure sensor that senses a fluid pressure drop over anorifice while the fluid is being emitted from the nozzle, the pressuresensor being in communication with the controller for determining afluid shear viscosity.
 24. A system as defined in claim 23, wherein theorifice is contained in the nozzle.
 25. A system as defined in claim 23,wherein the orifice is positioned upstream from the nozzle.
 26. A systemas defined in claim 21, wherein the system includes a tortuous pathlocated between the supply reservoir and the nozzle and wherein thesystem further comprises a pressure sensor that senses a pressure dropover the tortuous path, the pressure sensor being in communication withthe controller for calculating a fluid extensional viscosity.
 27. Asystem as defined in claim 26, wherein the tortuous path comprises apacked bed.
 28. A system as defined in claim 21, further comprising aflow meter that determines the flow rate of the fluid as it is pumpedfrom the supply reservoir, the flow meter being in communication withthe controller.
 29. A system as defined in claim 21, further comprisinga temperature sensor for sensing the temperature of the fluid within thesupply reservoir.
 30. A system as defined in claim 21, wherein thecontroller is configured to convert the spray pattern vibration outputreceived from the vibration sensor into a spectral density that is usedto calculate a power spectrum, the power spectrum being compared to apower spectrum of the known reference fluid.
 31. A system as defined inclaim 21, further comprising a spray chamber into which the fluid isemitted exiting the nozzle, the system further comprising an opticalsensor for optically inspecting a flow pattern being emitted from thenozzle.
 32. A system as defined in claim 1, wherein the vibration sensorcomprises an accelerometer.
 33. A system as defined in claim 21, whereinthe controller comprises at least one microprocessor.